WISE-CASING: Containment and Monitoring Institute (CaMI), Calgary, Canada FEM-DC Model

For the model calculation we applied EM3D using completion diagram of CaMI site and a background resistivity consistent with the borehole logs. It was also important to use the accurate position of the return electrode. We note that for the data fit the code also incorporated well casings for well INJ and the other observation well, either OB1 or OB2, in the calculation. In summary, we demonstrate here, for this particular case, that the DC results may be a reasonable approximation to the low frequency EM data collected at CaMI. If this approximation continues to hold, then the extreme computational efficiency offered by the hierarchical modeling used in the DC simulations will permit us to explore far more model complexity, especially the pervasive and troublesome data artifacts that arise when doing EM surveys in mature, culturally developed sites. In Brief, both the low frequency and DC simulation codes provided very consistent results that match the field data really well, indicating their capability to help monitoring borehole integrity with the low frequency EM method.

模型计算中，我们采用EM3D方法，使用CaMI场地的完井图及与钻孔测井数据一致的背景电阻率。同时，使用返回电极的精确位置也至关重要。我们注意到，在数据拟合过程中，代码还将INJ井及其他观测井（OB1或OB2）的井筒套管纳入计算。综上，针对此特定案例，我们证明直流（DC）结果可作为CaMI场地采集的低频电磁（EM）数据的合理近似。若该近似关系持续成立，则直流模拟中分层建模所带来的极高计算效率，将使我们能够探索更为复杂的模型，尤其是在成熟且人为干扰严重的场地进行电磁测量时出现的普遍且棘手的数据伪影。简言之，低频与直流模拟代码均给出了与现场数据高度一致的结果，表明它们具备通过低频电磁方法辅助监测钻孔完整性的能力。